The thermal transfer recording of the dye transfer type is a recording method in which a thermal transfer sheet having a colorant layer containing a thermally transferable dye formed on a base film is overlaid on an image-receiving sheet having a dye-receiving layer on its surface and in which the thermal transfer sheet is heated to transfer the dye in the thermal transfer sheet onto the image-receiving sheet, thereby effecting recording. Since this recording method enables a gradation expression by controlling a transfer amount of the dye by a level of thermal energy, it is applied to full color image recording in a video printer or the like.
In such thermal transfer recording of the dye transfer type, the dye to be used for the transfer sheet and the dye used in an ink composition for the transfer sheet considerably affect the speed of the transfer recording, the image quality and storage stability of a recorded product, and others, and properties of the dye are thus very important. The dye is required to meet the following conditions.
1) Easy sublimation and/or thermal diffusion under an operating condition of a thermal recording head.
2) No thermal decomposition under an operating condition of a thermal recording head.
3) Possession of a preferable hue for color reproduction.
4) A large molecular extinction coefficient.
5) Stability to heat, light, moisture, chemicals, and so on.
6) Easy synthesis.
7) Excellent suitability for formation of an ink.
8) No safety problem.
Heretofore, it is known to use an arylidene pyrazolone type dye represented by the general formula (I) as a dye for thermal transfer recording in a sublimation system among dyes to be used for such thermal transfer recording (cf. Patent Documents 1 to 3, for example). In addition, it is also known to use a combination of an arylidene pyrazolone type dye with a specific dicyanomethine type yellow dye, and a combination of an arylidene pyrazolone type dye with a specific pyridone azo type yellow dye (cf. Patent Documents 2 and 3).
Furthermore, it is known to use a bispyrazolone methine type dye represented by the general formula (II) as a dye for thermal transfer recording in the sublimation system, and it is described to use a combination of a bispyrazolone methine type dye with a specific pyrazolone azo type yellow dye, a combination of a bispyrazolone methine type dye with a specific pyridone azo type yellow dye, a combination of a bispyrazolone methine type dye with a specific quinophthalone type yellow dye, and a combination of three kinds of specific dyes including a bispyrazolone methine type dye (cf.
Patent Documents 4 to 7, for example).
Patent Document 1: JP-A-2-3450
Patent Document 2: JP-A-4-265792
Patent Document 3: JP-A-4-275184
Patent Document 4: JP-A-10-864
Patent Document 5: JP-A-10-181224
Patent Document 6: JP-A-10-203029
Patent Document 7: JP-A-2000-103174